SARMSARMSteroidalMyostatin inhibitorOral

YK-11 (myostatin-related, not a true SARM)

Also known as YK11 · YK-11

Written by enwyReviewed 15 Jul 20261 sources0 comments

YK-11 is a synthetic steroidal compound often grouped with SARMs but structurally a steroid derived from DHT. Its main proposed action is inhibition of myostatin signalling via follistatin, based only on cell-culture work. There is no human data; all effects and risks are preclinical or anecdotal, and it carries steroid-like suppression and possible hepatotoxicity.

01 Overview

YK-11 is a 5-alpha-reduced steroidal molecule that acts as a partial androgen-receptor agonist and, in myoblast cell studies, increases follistatin and thereby antagonises myostatin, the negative regulator of muscle growth. This myostatin angle drives its recreational appeal.

Because it is a steroid rather than a classic non-steroidal SARM, its safety profile is expected to resemble oral steroids more than mild SARMs, including suppression and potential liver strain. No clinical trials exist; dosing is entirely anecdotal and the compound is prohibited in sport and unapproved as a medicine.

02 Mechanism

Steroidal partial androgen-receptor agonist; in vitro it raises follistatin expression, inhibiting myostatin and potentially promoting muscle growth.

03 Dosing

Tier	Dose	Route	Notes
Light	5–10 mg/day	Oral	Anecdotal only; no validated dose exists.
Common	10–15 mg/day	Oral	Higher anecdotal range; risks poorly characterised.

Ester comparison

Ester	Half-life	Injection freq.	Testosterone by mass

04 Effects

Effect	Magnitude	Evidence
Myostatin inhibition via follistatinCell-culture studies show increased follistatin and muscle-cell differentiation; not shown in living humans.		Preclinical
Increased muscle massUsers report size and fullness gains; entirely uncontrolled data.		Anecdotal

05 Side effects

Effect	Severity	Frequency	Evidence
Testosterone suppressionAs a steroidal androgen-receptor agonist, YK-11 is expected to suppress endogenous testosterone.	Moderate	Common	Anecdotal
Possible hepatotoxicityBeing a steroidal compound, liver strain is plausible; no human data confirm or quantify risk.	Moderate	Unknown	Anecdotal
Joint and tendon discomfortSome users report dry or achy joints; mechanism unclear and unverified.	Mild	Uncommon	Anecdotal

06 Legal status

United States

Not FDA-approved; unlawful as dietary supplement

as of

United Kingdom

Not licensed as a medicine

as of

07 References

YK-11 induces follistatin and myogenic differentiation in myoblastsPubMed

08 Discussion0 comments

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This page is reference information, not medical advice. Doses and protocols are documented as they appear in the clinical literature and in practice — describing them is not a recommendation to use them. Countermeasures listed here are not a substitute for a physician. Legal status varies by jurisdiction and changes.